Method of grinding strong base ion exchange resins in the hydroxide form



Nov. 5, 1968 J. A. LEVENDUSKY METHOD OF GRINDING STRONG BASE ION EXCHANGE RESINS IN THE HYDROXIDE FORM Filed Jan. 30, 1964 United States Patenti() 3409 566 Y METHOD oF GRrNbrN; STRONG BASE 10N EgllANGE RESINS IN THE HYDROXIDE Joseph A. Levendusky, Bayonne, NJ., assgnor to Union Tank'Car Company, Chicago, Ill., a corporation of Delaware Filed `lan. 30, 1964, Ser. No. 341,847 5 Claims. (Cl. 260--2.1)

This invention relates to ion exchange resin particles in the size range of about 60 to 400 mesh and, more particularly, to a method of making strong base, divinylbenzene-styrene copolymer anion exchange resin particles (hereinafter called resin particles) in the hydroxide form and in the size range of about 60 to 400 mesh. As is well known in the art, strong base resin particles refers to resin particles having quaternary ammoniumras the principal functional group. 4 I

Heretofore hydroxide-form resin particles having a size range of about 60 to 400 mesh have been manufactured by grinding chloride-form resin particles in the size range of about 20 to 50 mesh and subsequently converting the ground chloride-form resin particles to the hydroxide form (by contacting them with a suitable aqueous alkaline hydroxide solution. This method of manufacturing hydroxide-form resin particles in the size range of about 60 to 400 mesh is not entirely satisfactory as the resin particles containV entrapped chloride ions. When the resin particles are used to treat a liquid stream, such as a condensate water, the chloride ions are released and appear in the eiiluent. It is theorized that during the grinding of these resiny particles portions of the resin matrix collapse and entrap some of the chloride ions. The entrappedchloride ions in the matrix,.for the' most part, are not affected when the resin particles are subsequently converted from Vthe chloride form to the hydroxide form. However, during prolonged use of the resin particles the chloride, ions have an opportunity to escape and will appear as an impurity in the efiluent, Furthermore, the resin particles made in this manner have a comparatively low capacity, i.e., ability to remove anions from an acid solution.

In an effort to avoid these problems, hydroxide-form resin particles having a size range of about 20 to 50 meshy have lbeen ground to the size range of about 60 to 400 mesh. Resin particles manufactured in this manner have been even less desirable, however, since they have low basicity, low capacity and/or an excess of fines (i.e., extremely small particles which substantially increase the pressure drop across a layer of the resin particles). It is therefore desirable tol provide a method of making hydroxide-form resin particles in the size range of about 60 to`-400 mesh from the same type of resin particles in the Size range of about 20 to 50 mesh, the resin particles so produced having high basicity and capacity and a relatively small amount of fines.

A It is an object of the present invention to provide a method of making hydroxide-form resin particles in the size range of about 60 to 400 mesh.

It is a further object to provide amethod of making hydroxide-form resin particles in the size range of about 60 to 400 mesh which will not release chloride .groups during treatment of liquid streams.

It is another object to provide a method of making hydroxide-form resin particles in the size range of about 60 to 400 mesh having high basicity and capacity.

Another object is to provide a method of making hydroxide-form resin particles in the size range of about 60 to 400 mesh that do not produce large pressure drops in uid streams because of excessive fines.

These and other objects more apparent hereinafter are realized by the method of the present invention wherein hydroxide-form resin particles in the size range of about "ice ' 60 to 40() mesh and having high basicity and capacity are made by adjusting the free water content of hydroxideform resin particles in the size range of about 20 to 50 mesh to within the range of about 1.9 to 7.6% by weight of the resin particles and grinding these resin particles in a hammer mill to the size range of about 60 to 400 mesh. It is preferred that the free water content of the resin particles prior to grinding be within the range of about 2 to 5% by weight of the resin particles.

The invention, both as to its organization and method of operation, taken vwith further objects andy advantages thereof, will be understood by reference to the following description taken in yconjunction with the accompanying drawing, in which:

The figure is a graph of the Basicity,' Capacity and Pressure Drop for Finely Divided vResin Particles.

For convenience, the resin particles in the size range of about 20 to 50 mesh will be referred to as'the large bead resin particles, while the resin particles in the size range of about 60 to 400 mesh will be referred to as the finely divided resin particles.

Basicity referred to herein is the measure of the ability of the resin particles to split a neutral salt, expressed in milliequivalents of anions removed from the aqueous salt solution per gram of bone dry anion resin particles, This is a measure also of the ability of the resin particles to remove weak acids and silica from aqueous streams, which is extremely important in purifying steam condensate streams. Capacity as used herein refers to the ability of the resin particles to remove anions from an acid solution, expressed in milliequivalents of anions removed trom the acid solution per gram of bone dry anion resin particles.

As used herein, the term free water refers to the water that may be removed from resin particles with -a Buchner funnel arrangement in which a sample of resin particles of predetermined weight is placed on filter paper in the funnel. The funnel is attached to a vacuum pump or the like which is then actuated. This draws air through the resin particles whereby water is removed from the resin particles. This is continued for 10 minutes and then the sample weighed again. The weight loss is the free water and is essentially all of the water physically held on the surface and in the interstices of the resin particles. The free water content of the resin particles based on the total weight of the resin particles may then be easily calculated. This is to be contrasted with the chemically held or bonded water in the resin particles, which, together with the physically held water, constitutes the total water content as used herein.

Considering the present invention in greater detail, hydroxide-form resin particles are well known in the art in the large bead size. In accordance with the present invention the free water content of these large bead resin particles is adjusted, prior to grinding, whereby the free water content is in the range of about 1.9 to 7.6% by weight of resin particles, preferably in the range of about 2 to 5% by weight. It is therefore necessary to first determine the amount of free water in the resin particles by using the Buchner funnel in the manner described above.

In accordance with the present invention, if the large bead resin particles have a free water content of less than about 1.9% by weight of the resin particles, free water must be added to the resin particles prior to grinding. Similarly, if the free water content of the resin particles is greater than about 7.6%'by Weight of the resin particles, then free Water must be removed from the resin particles prior to grinding.

There are numerous methods by which free water may be added to the large bead resin particles, as will be readily understood by one with ordinary skill in the art.

Forexample, demineralizedl water may be sprayed over the resin -particles in' a sufiicientwamountaud for a sufficient length of time until the resin particles have .absorbed a sufficient amount to raise the free water content within the range of about 1.9 to 7-;6% by weight of resin particlesz-Thcre are, also, of course, numerous methods by.which' freewater may be removed"from the resin particles; For' example,`-dry heated 'air may be passed through the-resinparticles. The techniques for removing andadding free water'tothe large'bead resinparticles is afm'atter within' the ordinary skill of one in thefart and 'does not per sefconstitute a part of the present invention. f '1 HAfterfthe free water content 'of the large bead resin particles hasbeenyadjusted to within the range of about 1t91to 7.6% by'weight, -the large bead resinparticlesin accordance 'with'the present invention are ground inl a hammer mill towithin the size rangeofoOto 400 mesh. Any'hamrner mill may-be used andsuch are well known. It has been empirically determined that other types of mills, such ,-asfai'ball Vrnill,-are ineffective `in that they produce-finely.` divided resin particles oflowbasicityor large quantitiesfof fines. The-latter is undesirable because fines. produce, among other things, high pressure drops across a bed or layer of the finelydivided resin particles. An exemplary hammer mill is the Model A Pulva-Sizer made by Pulva Corporation, Perth Amboy, NJ. The size screen employed will be dependent, of course, upon the size in range of about 60 to 400 mesh desired and-the selection of the proper screen size is a matter within the ordinary skill of one in the art. The finely divided resin particles made in accordance with thepresent invention have many possible uses in the purification of liquids and gases. Of particular interest is the use of these finely divided resin particles as a pre-coat layer, with or without finely divided cation resin par ticles, on a filter screen. It has been found that such a pre-coated filter screen is extremely effective in purifying liquids and gases, and in particular in purifying condensate streams in the steam generating unit of an electrical power plant. Such use of resin particles made in accordance with the present invention is described in detail in applicants United States Patent No. 3,250,703, issued May l0, 1966, and assigned to the assignee f present invention.

. Some of the advantages of the present invention will be seen from the following examples:

EXAMPLE I Hydroxide-form resin particles in the size range of about 20 to 50 mesh were tested for free water content. A 50 gm. sample of these large bead resin particles was weighed out `and placed in a Buchner funnel. Air was sucked through the sample in the Buchner funnel by a vacuum pump for ten minutes to remove the free water held by the resin particles. The sample was then weighed. The loss in weight indicated the amount of free water held by these resin particles. The free water content of the resin particles was then calculated and was 3.1% by weight of resin particles.

, The total water content of these large bead resin particles was also determined in the following manner. Another 50 gm. sample of these large bead resin particles was weighed out, placed in an oven and dried at 105 F. to constant weight. The weight loss of the resin particles was a measure of all the water physically and chemically held by the resin particles. The large bead resin'particles' were found to have Ja total water content o f 62.1% by weight of resin particles. t

About 50y lbs. of these resin particles were fed into a Model A Pulva-Sizer hammer mill. The Pulva-Sizer mill utilized va`0.35 herringbone screen. The hammer mill ground the large bead resin particles to finely divided resin particles within the size range of about 100 to 400 mesh, a major portion by weight of the resin particles .4 being in the size range of about'200 to 400 mesh.l

A 50 gm. sample of the finely dividedfesin particles was weighed out', placed in an oven and dried at 105 F. to constant weight. The total water content' of the finely divided'resin particles was 58.5% by weight. of the resin particles. t

-The vfinelyv divided resin particles -were 'tested for free caustic content. A l0 gm. sampley was weighed out and placed-in a Buchner funnel. Poured over the sample were 200 c'c. of dimineralize'd water. The'water was sucked through the resin particles, collected and titrated with an acid solution. The water'did-not contain any'caustic and therefore the resin particles did not contain any free caustic.

' The basicity of the finely divided resin particles was also tested. One hundred millilitersof a 0.75 N aqueous solution of sodium chloride `was passed'through 10 gms. of thel finely divided resin particles 'and collected. The resin particles were rinsed with demineralized water, the rinse. water being collected and addedV to the sodium chloride solution. The mixture was titrated with an acid to determine the quantity of hydroxide ions that had`been exchanged for chloride ions in the sodium chloride solution. In this manner, it was determined that the basicity of these nely divided resin particles was 4`.74 milliequivalents of chloride ions removed per gram of bone dry resin particles. The capacity of these resin particles was determined by passing ml. of a 1.0 N hydrochloric acid solution through 10 gms. of the resin particles. The resin particles were rinsed and the rinse water mixed with the' efiiuent hydrochloric acid. The mixture was titrated with a base to determine the milliequivalents of chloride ions remaining in the solution. With this information the milliequivalents of'chloride ion that had been removedY from the acid solution were calculated. In this manner the capacity ofthese resin particles was found to be 4.82 milliequivalents of chloride ions per gram of bone dry resin particles. Twenty grams of these finely divided anion resin partif cles were mixed with 20 gms. of strong acid, divinyl-benzene-styrene copolymer-type, hydrogen-form'cation resin particles in the size range of about V to 400 mesh. The mixture of finely divided resin particles were pre-coated on an annular cotton-wound filter screen having a surface area of l0.4 square feet. The pre-coat layer had a thickness of about 3716 inch. A 0.75 N sodium chloride solution was passed through the filter screen and pre-coat layer at a rate of 4'g.p.rn. per sq. ft. of surface) area. The pres-4 sure drop was 0.85 p.s.i., which indicates that excessive fines were not produced during the grinding operation. The conductivity of the eliiuent was measured continually. When the efiiuent conductivity had reached 0.5 mmhos the run was terminated. The operating capacity was then calculated andrdetermined to be 3.05 milliequivalentsfof chloride ions removed per gram of bone dry anion resin t' 1 par c es EXAMPLE n Hydroxide-,form resin particles in the size range of about 20 to 50 mesh were dried in a vacuum drier. This drier comprised an 18-inch diameter cylindrical chamber having la ylength of 37 inches. Mounted therein were three trays having a total area of 9 square feet. Each tray had copper tubing soldered to the bottom thereof, the copper tubing being connected to a hot water circulating system. The unit was loaded with 77 lbs. of the large bead resin particles and heat and vacuum applied. The unit was operated at a pressure of 27 inches of Hgand 138 F. Water was circulatedvin the tubing for a lperiod of 17 hours. Steam was then used as the heating medium and the pressure was lowered to 22 inches of Hg. The steam was at a temperature of 212 yF. and was used in the coils of the drier for a .period of 5V: hours. The unit was then shut down at vthis point and the top tray removed. The material from the top tray was found to have a total water content of 57.4% by weight `of the resin particles.

The other tw'o'trayswere left in the drier and dried for an additional 25% hours at 25 inches of Hg with 212 F. steam. The .large bead resin particles dried in this manner on the lower two trays had a total water content of 31.1%

III establish that the free water content should not exceed about 7.6% Iby weight of the resin particles.v

. EXAMPLE IV Hydroxide-form resin particles in the size range of The large bead resin particles from the bottom trays l were tested and ground in the .Same manneland with the about 20 to 50 mesh were tested for free water content equipment as the large bead resins in Example 1 The in the same manner as 1n Example I. The free water con-l results are tabulated below in Table A: tent of the large bead resin particles was found to be about 4% by weight of resin particles. j v Table A The total water content of large bead resin particles Total water content large bead particles, Wt. per- 10 was determined in the same manner as in Example I. The Cent 31.1' total Water content of these resin particles was found t0 Free water content large bead particles, wt. perbe about 63% by weight of the resin particles.

cent 27.9 About 4,000 lbs. of these large bead resin particles were Total water content lfinely divided particles, Wt. fed into the Model A Pulva-Sizer mill used in Example I.' percent y 28.5 The mill ground the large bead resin particles to within Free caustic, med/gm. of dry particles 0.01 the size range of about 100 to 400 mesh, the major por- Basicity, meq./gm. of dry particles 3.0 tion of the resin particles by weight being in the size range Capacity, meq./ gm. of dry particles 3.7 of about 200 to 400 mesh. A sample of the finely divided Operating capacity, meq./ gm. of dry particles 1.3 20. resin particles was weighed and dried to constant weight Pilot run, pressure drop, p.s.i 0.2' in an oven at about 105 F. The weight loss of these It will be noted in Table A that the free water content rltrllcltlcles was the total Water content of the resm is expressed as a negative value. IThis means that the large The total Water content of these llnely divided resin bead resin. particles are substantially without free water Particles was about 57 58% ,by weight of resin partleles and contam 1 5S chemlcauy Pcund *Water than usually Mounted in a vertical tank having a diameter of five Present by the ludlcated uegatlvc Value feet and Ia height of six feet were 209 two-inch diameter annular cotton-wound filter screens each having a length EXAMPLE HI of 60 inches. The filter screens had a total surface area Eight othgr batches (referred to -as Bafches 3 10) of 30 of about 550 square feet. The finely divided resin partifinely divided resin particles were made and tested in the cles made iu accordance With this example Were mixed manner described in detail in Example I. In Batches 9 111 by weight with Strong acid, divinvl-benzene-Styrerlle and 10 the large bead resin particles were soaked in decopolymer-type, hydrogen-form cation exchange resins 1n mineralized water. In Batch 8 a predetermined amount of the size fange 0f about 10 0 t0 400 mesh- Each 0f the ltef water was added to large bead resin particles of the type screens Wes Pre-Coated Wlth the HuXtufe ef untill/ dlvlded used in Example I. With the exception of Batch 6, those fesm Partlcles- A slutty 0f me uely dlVlded reSlIl Partlbatches in this example that had a free water content of cles Was Pfc/Rated Wlth dcmmcfa'hled Water' The stuffy less than 3.1% were dried in the vacuum drier discussed Was Pumpcf1 mtO the. tank m'd thfcu'gh the filter screens, in Example II to the moisture content shown in Table the uely dlvlded resul Partlcles being dePcSlted upon the B below. In Batch 6 large bead resin particles made in 40 filter screens t0 form a Pfc-coat layef The Pfc-coat layer Example II from the top tray were mixed with large bead Was about M1 inch iu thicknessresin particles 0f the Same type as used in Example I, The feed stream being treated was steam condensate The results of these tests are tabulated in Table B water having chloride impurities of about 2,000l p.p.b. below: larid dissolved silica impurities in the range of to 200 TABLE B Batch 3 4 5 6 7 8 9 1 i0 Total water content large bead particles, wt. percent 37. 6 45.0 50.6 59. 9 60.9 66. 6 72.0 73. 0 Free Water content large bead particles, Wt. percent- -21. 4 14. 0 8. 4 0.9 1. 9 7.6 13. 0 14. 0 Total water content finely divided particles, wt. percent 34. 6 43. 5 49. 6 54.8 61. 0 65. 6 67. 5 68.3 Free caustic, med/gm. of dry particles 0 0 0 0 0 0 0 0 Basicity, meq./gm. of dry particles 3. 7 4. 0 4. 0 4.0 4. 6 4. 6 4. 9 4. 8 Capacity, meqJgm. of dry particles 3.8 4.1 4. 2 4. 7 4.4 4. 6 4.8 Operating capacity, meq./gm. of dry pa cles 1.4 1. 9 3. 0 3.0 3.0 3.0 Pilot run pressure drop, p.s.i 0.4 0.4 0.4 0.3 0.9 2. 1

1 The recovered finely divided resin particles were in paste form and could not be ground on a practical basis in the mill.

3 A Ms herringbone screen used.

The basicity, capacity and pressure drop data of Examples I, II and III were plotted and the curves are illustrated in FIGURE 1. It will be noted that if the large bead resin particles have less than about 1.9% by Weight free water content, that after grinding the basicity of the finely divided resin particles is substantially decreased. Accordingly, the basicity data of Examples -I, II arid III establish that in accordance with the present invention the free Water content of the large bead resin particles before grinding must be greater than about 1.9% by weight of the resin particles to obtain high basicity. Furthermore, as illustrated in the figure, the capacity of the iinely divided resin particles is also at its highest in this range, so that high capacity and basicity are achieved by the method of the present invention.

The pressure drop curve further demonstrates that when the free water content is greater than Iabout 7.6% by weight the production of fines is substantially increased and thereby causes undesirably high pressure drops. Accordingly, the pressure drop data of Examples I, Il and p.p.b. The condensate water was passed through the precoated iilter screens. The conductivity of the influent coridensate stream was about 5 to 6 mmhos due to the presence of the chloride impurities. The silica was measured by standard colorimetric procedures.

The conductivity of the elli-uent was initial-ly about 0.3 to 0.5 rnmho. The flow of condensate Water was terminated when the etiiuent had a conductivity in excess of 1.0 mmho. Simultaneously periodic samples of the etiluent were tested for silica content by standard colorimetric procedures. Every test showed that the eiiiuent contained less than 20 ppb. of silica, except toward the end of the run when the silica content went up to about 40-50 ppb. A known quantity of condensate water had therefore passed through the filter unit and had a known concentration of silica and chlorides. Knowing the concentration of silcia and chloride ions in the eliiuent, the operating capacity of these resin particles could be determined. The operating capacity was calculated to be about 2.9 milliequivalents of anion contaminants removed per gram of dry anion resin- -p-articles. This example 'substant-iated-that the finelydivided'resin particles made-in accordance with the present invention would yield an operating capacityv consistent with the laboratory test data of Examples I and lIII. v

HWhile -the embodiment described herein'is at present considered- 'tobe preferred, it' will be understood that various modifications and improvements may be made therein and itis intended to cover-inthe appended claims all '--such-modications and improvementsas fall Within the Atrue spi-rit andlscopelof the-invention.'

What is claimed is:

1. The method of makingwhydroxi'de-formstrong base, divinylbenzene-Istyrene copolymer :anion exchange resin particlesin the size range of 4about 60 to '400 mesh which comprises grinding in a hammer mill nhydroxidef-lorm strong ibase, divinylbenzene-styrene copolymer anion exchange'resinparticles in the -size range of'a'bout 20'-to 50 mesh having-afree water content' in the range-of about 1.9 to 7.6% by weight `of said resin particles.

`2. The method of claim 1 wherein said free .water content is inthe range of about 2'to 5% by weight of said resin particles.-

'3. 1The method of making hydroxide-form strong base, divinylbenzene-styrene copolymer anion exchange resin particles in the size range of about 60 to 400 mesh, said resin particles having high basicity and capacity, which comprises adjusting the free Water content of hydroxideform strong base, divinylbenz'e'ne-styreneY copolymer anion exchange lresin particles inthe size-range of about 20 to SO-meshv to within the-range -of -about.1.9-tto-7.6% lby weight of the vresin particles and Rgrinding'rsaidf vresin 1 particles in ya hammer mill tothe size range Aof about 60 formenMEFERENCES'- t l .DOWeXI 1011. YEX,clzinkge,` The D pw clienjnai mpany Midland, Michi, 1959,"p 7 3; I r Y. y

WLL-IAM SHORT; primitif-y Examinar! M. -GoLDsr-EIN, Assistant, Examiner.;v 

1. THE METHOD OF MAKING HYDROXIDE-FORM STRONG BASE, DIVINYLBENZENE-STYRENE COPOLYMER ANION EXCHANGE RESIN PARTICLES IN THE SIZE RANGE OF AOBUT 60 TO 400 MESH WHICH COMPRISES GRINDING IN A HAMMER MILL HYDROXIDE-FORM STRONG BASE, DIVINYLBENZENE-STYRENE COPOLYMER ANION EXCHANGE RESIN PARTICLES IN THE SIZE RANGE OF ABOUT 20 TO 50 MESH HAVING A FREE WATER CONTENT IN THE RANGE OF ABOUT 1.9 TO 7.6% BY WEIGHT OF SAID RESIN PARTICLES. 